Interval Analysis Method of Fatigue and Fracture Reliability for Offshore Structures Based on Probabilistic and Non-Probabilistic Hybrid Model

The concept of non-probabilistic reliability, which is to measure the reliability in terms of the amount of uncertainty consistent with the condition of no failure, is used to establish a new model for fatigue reliability analysis. Some of the uncertain parameters of structures are expressed as interval variables instead of random variables. In numerical example, fatigue lifetime of the tenders of tension leg platform is assessed using hybrid models of probabilistic and nonprobabilistic based on S-N approach and fracture mechanics approach. The new model overcomes the shortcoming of traditional probabilistic methods, which need large number of statistical data and huge computational efforts and it is effective and useful in formulating control laws in the absence of detailed probabilistic information for fatigue and fracture reliability analysis.